Manufacturing of L-ascorbic acid (Vitamin-C) is currently based on the synthesis developed by Reichstein and patented in 1936 (U.S. Pat. No. 2,056,126). Over the years, advances in science and technology have led to numerous technical modifications which have improved the efficiency in the production of Vitamin-C and have been incorporated into the Reichstein-Grussner synthesis which is the predominant method used in industry today. The Reichstein-Grussner synthesis involves five distinct steps: catalytic hydrogenation, bacterial fermentation, acid promoted reaction with acetone, catalytic oxidation, and acid hydrolysis (see Kirk-Othmer "Encyclopedia of Chemical Technology", 4th ed., John Wiley & Sons, New York, 1992). The steps of the aforementioned process are such that the synthesis requires the addition of various chemicals (including strong acids and bases), multiple stages of by-product separation, the treatment and disposal of environmentally toxic wastes, and extensive process control mechanisms. Accordingly, the synthesis is very costly. Thus, various attempts have been made to devise a new, more economical and efficient way to manufacture Vitamin-C.
To date, the prior art has concentrated on reducing the cost of synthesizing L-ascorbic acid by increasing the efficiency of, and reducing the cost of, a particular step in the Reichstein-Grussner synthesis. U.S. Pat. No. 2,190,377 to Dalmer et al. discloses a catalytic reaction for converting L-sorbose into 2-keto-L-gulonic acid ("L-KGA"). This method entails reacting an alkaline solution of sorbose with gaseous oxygen in the presence of platinum or palladium metal. This approach condenses two of the five steps of the Reichstein-Grussner synthesis into one step, but still leaves an intricate, multi-step process for vitamin-C synthesis.
U.S. Pat. No. 2,165,151 to Pasternack et al. discloses a method of oxidizing L-KGA to L-ascorbic acid without the use of strong acids or bases as is traditionally used in the last step of the Reichstein-Grussner synthesis. The method involves introducing fine metal filings, including cobalt, into an aqueous solution of KGA. The solution is then heated and agitated to reach fifty percent conversion to vitamin-C.
The foregoing and other alterations to the currently used Reichstein-Grussner synthesis have failed to eliminate aforementioned drawbacks of vitamin-C synthesis in a cost-effective manner so as to be commercially viable.
It is, therefore, an object of the invention to provide a single-step synthesis of L-ascorbic acid from D-glucose such that vitamin-C may be produced in a cost-effective manner.